This invention is directed to an improved process for the preparation of impact polystyrene wherein polybutadiene used in the process contains an optical brightener.
Impact polystyrene differs from polystyrene in that it contains a small amount of a rubbery polymer. The early forms of impact polystyrene were produced by mechanically blending polystyrene with the rubbery polymer, which was usually a styrene-butadiene polymer prepared by emulsion free radical polymerization. An improved method of preparing impact polystyrene required the rubbery polymer to be dissolved in the styrene monomer and the so-formed solution was subjected to polymerization. More recent requirements of the market place include the absence of discoloration for white grades of impact polystyrene.